Dilation system and method

BACKGROUND

1. Field of the Presently Disclosed Inventive Concepts

The inventive concepts disclosed and claimed herein relate to systems and methods for performing surgical procedures and, more particularly, but not by way of limitation, to systems and methods for accessing a surgical target site to perform surgical procedures.

2. Brief Description of Related Art

The present state of the art, when referencing a lateral surgical access approach, typically consists of using the following surgical instruments: neuromonitoring probe, dilators, and a retractor. Once an operative level is identified and an incision is created, dilators are used to create a surgical access site which is often followed by the use of a retractor or other specialized tools to create a surgical access corridor.

During a lateral approach to a patient's spine, a psoas muscle, which is located on either side of the spine, is separated in order to access the spine and, in particular, an intervertebral disc space or one or more vertebral bodies within a patient's spinal column. It is desirable to avoid neural elements or nerves of the lumbar plexus that lie within the psoas muscle during such procedures. The anterior third of the psoas muscle is typically considered a safe zone for muscle separation.

The neural elements or nerves of the psoas muscle may be mapped using a stimulating probe. In this manner, the most posterior neural or nerve-free area of the psoas muscle may be located and identified. The stimulating probe may then be inserted through the psoas muscle via the most posterior neural or nerve-free tissue area or through nearly any other region that is free of neural elements or nerves and toward the spine or into the intervertebral disc space in order to initiate safe tissue separation of the psoas muscle. Dilators are next placed over the probe to create and enlarge a surgical access site. Following the use of dilators, a retractor or other specialized tools are used to further enlarge the surgical access corridor.

Concentric dilators separate the muscle radially, and as such, dilate tissue on all both sides of the stimulating probe in a uniform fashion. This in turn may impinge on neural elements or nerves located outside of the safe zone. Directional dilators have been suggested to overcome the problems associated with concentric dilators. While directional dilation systems are effective for avoiding known neural elements, they are limited in their ability to continuously monitor nerve proximity and to create a surgical access site of a desired shape while at the same time reducing the amount of tissue damage.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist those of ordinary skill in the relevant art in making and using the inventive concepts disclosed herein, reference is made to the appended drawings and schematics, which are not intended to be drawn to scale, and in which like reference numerals may refer to the same or similar elements for consistency. For purposes of clarity, not every component may be labeled in every drawing. Certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. In the drawings:

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of an embodiment of a dilation system constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 2</figref> is a top plan view of the dilation system of <figref idref="DRAWINGS">FIG. 1</figref>.

<figref idref="DRAWINGS">FIG. 3</figref> is a perspective view of a first dilator constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 4</figref> is a top plan view of the first dilator of <figref idref="DRAWINGS">FIG. 3</figref>.

<figref idref="DRAWINGS">FIG. 4A</figref> is a top plan view of another embodiment of a first dilator constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 5</figref> is a perspective view of a second dilator constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 6</figref> is a top plan view of the second dilator of <figref idref="DRAWINGS">FIG. 5</figref>.

<figref idref="DRAWINGS">FIG. 7</figref> is a perspective view of a third dilator constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 8</figref> is a top plan view of the third dilator of <figref idref="DRAWINGS">FIG. 7</figref>.

<figref idref="DRAWINGS">FIGS. 9A-9F</figref> illustrate a method of using the dilation system to dilate a surgical opening in a psoas muscle.

<figref idref="DRAWINGS">FIG. 10</figref> is a top plan view of another embodiment of a dilation system constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 11</figref> is a top plan view of a first dilator of the dilation system of <figref idref="DRAWINGS">FIG. 10</figref>.

<figref idref="DRAWINGS">FIG. 12</figref> is a top plan view of a second dilator of the dilation system of <figref idref="DRAWINGS">FIG. 10</figref>.

<figref idref="DRAWINGS">FIG. 13</figref> is a top plan view of a third dilator of the dilation system of <figref idref="DRAWINGS">FIG. 10</figref>.

<figref idref="DRAWINGS">FIG. 14</figref> is a top plan view of another embodiment of a dilation system constructed in accordance with the inventive concepts disclosed herein.

<figref idref="DRAWINGS">FIG. 15</figref> is a top plan view of a first dilator of the dilation system of <figref idref="DRAWINGS">FIG. 14</figref>.

<figref idref="DRAWINGS">FIG. 16</figref> is a top plan view of a second dilator of the dilation system of <figref idref="DRAWINGS">FIG. 14</figref>.

<figref idref="DRAWINGS">FIG. 17</figref> is a top plan view of a third dilator of the dilation system of <figref idref="DRAWINGS">FIG. 14</figref>.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following detailed description of embodiments of the inventive concepts, numerous specific details are set forth in order to provide a more thorough understanding of the inventive concepts. However, it will be apparent to one of ordinary skill in the art that the inventive concepts disclosed and claimed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the instant disclosure.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements or steps is not necessarily limited to only those elements or steps and may include other elements, steps, or features not expressly listed or inherently present therein.

Unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the inventive concepts. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Throughout this disclosure and the claims, the terms “about,” “approximately,” and “substantially” are intended to signify that the item being qualified is not limited to the exact value specified, but includes some slight variations or deviations therefrom, caused by measuring error, manufacturing tolerances, stress exerted on various parts, wear and tear, or combinations thereof, for example.

The use of the term “at least one” will be understood to include one as well as any quantity more than one, including but not limited to each of, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, and all integers therebetween. The term “at least one” may extend up to 100 or 1000 or more, depending on the term to which it is attached; in addition, the quantities of 100/1000 are not to be considered limiting, as higher limits may also produce satisfactory results. Singular terms shall include pluralities and plural terms shall include the singular unless indicated otherwise.

The term “or combinations thereof” as used herein refers to all permutations and/or combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof” is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AAB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

Finally, as used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily referring to the same embodiment, although the inventive concepts disclosed herein are intended to encompass all combinations and permutations including one or more of the features of the embodiments described herein.

As generally understood by one of ordinary skill in the art, dilation systems will be described in detail herein in connection with accessing the spine or performing a surgical procedure, but dilation systems according to the inventive concepts disclosed herein may find use in any desired orthopaedic or other surgical procedures in which a surgeon wishes to gain access to an internal cavity by cutting the skin and going through the body wall in order to keep the incision spread apart so that surgical instruments can be inserted in the internal cavity. For example, dilation systems according to the inventive concepts disclosed herein may be used for anteriorly or posteriorly accessing the spine, for accessing the thoracic or cervical region of the spine, or for accessing any other part, cavity, or organ of the body of a human being or an animal.

Embodiments of dilation systems according to the inventive concepts disclosed herein may be used to gradually and atraumatically dilate a surgical opening by sequentially inserting two or more serial dilators into the surgical opening and rotating the dilators to enlarge the surgical opening. In some embodiments, the surgical opening may be enlarged by inserting a first dilator, rotating the first dilator, and inserting one or more second dilators over the first dilator, with each subsequent dilator being rotated to dilate the surgical opening. Further, in some embodiments dilations systems according to the inventive concepts disclosed herein may include reduced diameter dilators with standard or fixed-size stimulating probes.

Referring to <figref idref="DRAWINGS">FIGS. 1-2</figref>, an embodiment of a dilation system <b>100</b> is illustrated. The dilation system <b>100</b> includes a first or initial dilator <b>102</b>, one or more second or intermediate dilators <b>104</b>, and a third or final dilator <b>106</b> configured to be matingly coupled with one another around a longitudinal axis <b>108</b>. It is to be understood that dilation systems according to the inventive concepts disclosed herein may include any desired number of dilators, such as two, three, four, or more dilators. The dilation system <b>100</b> is configured to be used in combination with a monitoring K-wire or stimulating probe, such stimulating probe <b>170</b> depicted in <figref idref="DRAWINGS">FIG. 9A</figref>, for transmitting an electrical pulse as described below.

Referring now to <figref idref="DRAWINGS">FIGS. 3-4</figref>, the first dilator <b>102</b> includes an elongated body <b>110</b> having a longitudinal axis <b>112</b>, a proximal end <b>114</b> a distal end <b>116</b>, and an outer surface <b>118</b>. The elongated body <b>110</b> may include a bore <b>120</b>. The elongated body <b>110</b> has a substantially elliptical transverse cross-section and includes a major axis <b>122</b> and a minor axis <b>124</b> which are substantially normal to one another (e.g., substantially perpendicular to one another). The elongated body <b>110</b> has a first diameter (e.g., a transverse diameter) along the major axis <b>122</b> and a second diameter (e.g., a conjugate diameter) along the minor axis <b>124</b>, with the first diameter being greater than the second diameter.

The outer surface <b>118</b> may include at least one channel <b>126</b> formed therein and extending along the outer surface <b>118</b> from the proximal end <b>114</b> to the distal end <b>116</b>. The channel <b>126</b> is configured to slidably receive a stimulating probe, such as a stimulating probe <b>170</b><i>a </i>depicted in <figref idref="DRAWINGS">FIG. 9B</figref>). The channel <b>126</b> may extend along the outer surface <b>118</b> such that the channel <b>126</b> intersects the major axis <b>122</b> of the elongated body <b>110</b> in some embodiments. It is to be understood that in some embodiment the channel <b>126</b> may intersect the minor axis <b>124</b>, may be tangental or positioned adjacent to the major axis <b>122</b> or the minor axis <b>124</b>, and/or may be positioned so as not to intersect either the major axis <b>122</b> or the minor axis <b>124</b>. Further, any number of channels <b>126</b> may be implemented with the first dilator <b>102</b> in some embodiments of the inventive concepts disclosed herein, such as two or more channels <b>126</b>. In some embodiments where multiple channels <b>126</b> are implemented, one or more first channels <b>126</b> may intersect the major axis <b>122</b>, and one or more second channels <b>126</b> may intersect the minor axis <b>124</b> as will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure.

The outer surface <b>118</b> may taper inwardly adjacent to the distal end <b>116</b> so that the first dilator <b>102</b> is configured to minimize trauma to tissues when the distal end <b>116</b> of the first dilator <b>102</b> is inserted into a tissue. In some embodiments, the outer surface <b>118</b> may include a plurality of grasping notches <b>128</b> formed therein adjacent to the proximal end <b>114</b> of the elongated body <b>110</b>. The grasping notches <b>128</b> may be configured to allow a surgeon to grip the first dilator <b>102</b> (e.g., manually or via a suitable surgical tool or robotic arm) and to manipulate the first dilator <b>102</b> as will be described below.

Referring again to <figref idref="DRAWINGS">FIG. 1</figref>, the elongated body <b>110</b> of the first dilator <b>102</b> is sized relative to the second dilator <b>104</b> such that a portion of the elongated body <b>110</b> (e.g., the proximal end <b>114</b> and/or a portion of the outer surface <b>118</b> including the grasping notches <b>128</b>) remains accessible when the dilation system <b>100</b> is assembled and used as will be described below.

The bore <b>120</b> may extend through the elongated body <b>110</b> from the proximal end <b>114</b> to the distal end <b>116</b> and is configured to slidably receive a stimulating probe or a guide wire therein. In the embodiment shown in <figref idref="DRAWINGS">FIGS. 3-4</figref>, the bore <b>120</b> is substantially aligned with the longitudinal axis <b>112</b>. However, in some embodiments, the bore <b>120</b> may be laterally offset from the longitudinal axis <b>112</b> or omitted. It is to be understood that while the bore <b>120</b> is shown as being substantially cylindrical in shape, the bore <b>120</b> may have any desired shape, size, and cross-section in some embodiments of the inventive concepts disclosed herein. For example, as shown in <figref idref="DRAWINGS">FIG. 4A</figref>, an embodiment of a first dilator <b>102</b><i>a </i>may be implemented similarly to the first dilator <b>102</b> and may include a bore <b>120</b><i>a </i>which is offset from the longitudinal axis <b>112</b><i>a. </i>

The first dilator <b>102</b> may be constructed of any desired material, such as stainless steel, surgical steel, titanium, metals, anodized aluminium, non-metals, polyether ether ketone (PEEK), polymers, resins, or combinations thereof, and may be constructed using any desired manufacturing technique, such as machining, casting, molding, or combinations thereof. In some embodiments, the first dilator <b>102</b> may be provided visual or haptic depth markings (e.g., along the outer surface <b>118</b>) to indicate an appropriate insertion depth to a surgeon as will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure.

Referring now to <figref idref="DRAWINGS">FIGS. 5-6</figref>, the second dilator <b>104</b> may be implemented similarly to the first dilator <b>102</b> and includes an elongated body <b>130</b> having a longitudinal axis <b>132</b>, a proximal end <b>134</b>, a distal end <b>136</b>, an outer surface <b>138</b> extending between the proximal end <b>134</b> and the distal end <b>136</b>, and a bore <b>140</b> extending from the proximal end <b>134</b> to the distal end <b>136</b>. The elongated body <b>130</b> has a substantially elliptical transverse cross-section and includes a major axis <b>142</b> and a minor axis <b>144</b> being substantially normal (e.g., substantially perpendicular) to the major axis <b>142</b>. The elongated body <b>130</b> has a first diameter (e.g., a transverse diameter) along the major axis <b>142</b> and a second diameter (e.g., a conjugate diameter) along the minor axis <b>144</b>, with the first diameter being greater than the second diameter.

The bore <b>140</b> is sized, shaped, and configured to matingly and slidably receive the first dilator <b>102</b> therein so that the major axis <b>142</b> of the second dilator <b>104</b> is aligned with the minor axis <b>124</b> of the first dilator <b>102</b> and the minor axis <b>144</b> of the second dilator <b>104</b> is aligned with the major axis <b>122</b> of the first dilator <b>102</b>.

The outer surface <b>138</b> has at least one channel <b>146</b> for receiving a stimulating probe, the channel <b>146</b> extending from the proximal end <b>134</b> to the distal end <b>136</b> and intersecting the major axis <b>142</b> of the elongated body <b>130</b>. It is to be understood that in some embodiments, the channel <b>146</b> may intersect the minor axis <b>144</b>, may be tangental or positioned adjacent to the major axis <b>142</b> or the minor axis <b>144</b>, and/or may be positioned so as not to intersect either the major axis <b>142</b> or the minor axis <b>144</b>. Further, any number of channels <b>146</b> may be implemented with the second dilator <b>104</b> in some embodiments of the inventive concepts disclosed herein, such as two or more channels <b>146</b>. In some embodiments where multiple channels <b>146</b> are implemented, one or more channel <b>146</b> may intersect the major axis <b>142</b>, and one or more channel <b>146</b> may intersect the minor axis <b>144</b> as will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure.

The outer surface <b>138</b> may taper adjacent to the distal end <b>136</b> so as to facilitate insertion into tissue. The general shape of the first dilator <b>102</b> is atraumatic. In some embodiments, the outer surface <b>138</b> may include a plurality of grasping notches <b>148</b> formed therein adjacent to the proximal end <b>134</b> of the elongated body <b>130</b>. The grasping notches <b>148</b> may be configured to allow a surgeon to grip the second dilator <b>104</b> (e.g., manually or via a suitable surgical tool) and to manipulate the second dilator <b>104</b> as will be described below.

Referring again to <figref idref="DRAWINGS">FIG. 1</figref>, the elongated body <b>130</b> of the second dilator <b>104</b> is sized relative to the third dilator <b>106</b>, such that a portion of the elongated body <b>130</b> (e.g., the proximal end <b>134</b> and/or a portion of the outer surface <b>138</b> including the grasping notches <b>148</b>) remains accessible when the dilation system <b>100</b> is assembled and used as will be described below.

As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, any desired number of second or intermediate dilators <b>104</b> may be implemented with the dilation system <b>100</b>, such as one, two, three, or more of the second dilators <b>104</b>. For example, where multiple second dilators <b>104</b> are implemented with an embodiment of the dilation system <b>100</b>, each successive second dilator <b>104</b> may have a bore <b>140</b> configured to matingly (e.g., slidably) receive a preceding second dilator <b>104</b> therein such that the major axis <b>142</b> of one of the preceding second dilator <b>104</b> is substantially aligned with a minor axis <b>144</b> of the successive second dilator <b>104</b> and the minor axis <b>144</b> of the preceding second dilator <b>104</b> is substantially aligned with the major axis <b>142</b> of the successive second dilator <b>104</b>.

Referring now to <figref idref="DRAWINGS">FIGS. 7-8</figref>, the third dilator <b>106</b> may be implemented similarly to the first dilator <b>102</b> and includes an elongated body <b>150</b> having longitudinal axis <b>152</b>, a proximal end <b>154</b>, a distal end <b>156</b>, an outer surface <b>158</b> extending between the proximal end <b>154</b> and the distal end <b>156</b>, and a bore <b>160</b> extending from the proximal end <b>154</b> to the distal end <b>156</b>. The elongated body <b>150</b> is illustrated as having a substantially circular transverse cross-section and is configured so as to allow the third dilator <b>106</b> to interface with a retractor, such as a multi-blade retractor in some embodiments.

The outer surface <b>158</b> may include at least one channel <b>166</b> for receiving a stimulating probe therein. The channel <b>166</b> may extend from the proximal end <b>154</b> to the distal end <b>156</b> and may be positioned so as to intersect the minor axis <b>144</b> of the elongated body <b>130</b> when the second dilator <b>104</b> is matingly received in the third dilator <b>106</b>. It is to be understood that in some embodiment the channel <b>166</b> may be tangental or positioned adjacent to the major axis <b>142</b> and/or may be spaced a distance from the major axis <b>142</b>. Further, any number of channels <b>166</b> may be implemented with the third dilator <b>106</b> in some embodiments of the inventive concepts disclosed herein, such as two or more channels <b>166</b>.

The outer surface <b>158</b> may taper adjacent to the distal end <b>156</b> so as to facilitate insertion into tissue. The general shape of the second dilator <b>104</b> is atraumatic. In some embodiments, the outer surface <b>158</b> may include a plurality of grasping notches <b>159</b> formed therein adjacent to the proximal end <b>154</b> of the elongated body <b>150</b>. The grasping notches <b>159</b> may be configured to allow a surgeon to grip the third dilator <b>106</b> (e.g., manually or via a suitable surgical tool) and to manipulate the third dilator <b>106</b> as described below.

The bore <b>160</b> has a substantially elliptical transverse cross-section and includes a major axis <b>162</b> and a minor axis <b>164</b>, which may be substantially normal to one another. The bore <b>160</b> has a first diameter (e.g., a transverse diameter) along the major axis <b>162</b> and a second diameter (e.g., a conjugate diameter) along the minor axis <b>164</b>, with the first diameter being greater than the second diameter. The bore <b>160</b> is configured to matingly and slidably receive the second dilator <b>104</b> therein such that the major axis <b>142</b> of the elongated body <b>130</b> is aligned with the major axis <b>162</b> of the bore <b>160</b> and such that the minor axis <b>144</b> of the elongated body <b>130</b> is aligned with the minor axis <b>164</b> of the bore <b>160</b>.

As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, in some embodiments the third dilator <b>106</b> may be omitted, while in some embodiments multiple third dilators <b>106</b> may be implemented, with each successive third dilator <b>106</b> having a bore <b>160</b> configured to matingly receive a preceding third dilator <b>106</b> therein.

Referring now to <figref idref="DRAWINGS">FIGS. 9A-9F</figref>, an exemplary embodiment of a method of using the dilation system <b>100</b> to access a lumbar region of a spine via a lateral approach will be described herein. However, a similar or the same method may be used with the dilation system <b>100</b> in other parts of a patient's body.

Using a stimulating probe <b>170</b> and an electromyograph (EMG) (not shown) in a manner similar to that described in U.S. Publication No. 2011/0208226, which is hereby expressly incorporated herein by reference in its entirety, a surgeon may map a safe zone (e.g., a zone generally free of neural elements or nerves) on a tissue of interest (e.g., psoas muscle). For example, on a human psoas muscle, the anterior third of the psoas muscle is generally considered a safe zone. Once a safe zone is established, anatomical placement may be confirmed via intra-operative fluoroscopy.

With a safe zone established, anatomical placement may be confirmed via intra-operative fluoroscopy. The surgeon inserts the stimulating probe <b>170</b> through the psoas muscle toward the patient's spine, as shown in <figref idref="DRAWINGS">FIG. 9A</figref>. If the surgery is being performed on the intervertebral disc space, the distal end of the stimulating probe <b>170</b> may be inserted into the annulus of the desired intervertebral disc space or may be positioned so that a tip of the stimulating probe <b>170</b> is proximate to the patient's spine <b>174</b>. The stimulating probe <b>170</b> may be inserted via the most posterior portion of the safe zone in some embodiments.

As shown in <figref idref="DRAWINGS">FIG. 9B</figref>, the surgeon may insert or slide the first dilator <b>102</b> over the stimulating probe <b>170</b> (e.g., such that the stimulating probe <b>170</b> is slidably received in the bore <b>120</b> of the first dilator <b>102</b>) and may insert the distal end <b>116</b> and/or a portion of the elongated body <b>110</b> of the first dilator <b>102</b> through the psoas muscle <b>172</b> and toward the patient's spine <b>174</b>. In some procedures, the first dilator <b>102</b> may be inserted through the psoas muscle without the use of a stimulating probe or guide wire. To minimize trauma to the psoas muscle <b>172</b> from the insertion of the first dilator <b>102</b> the first dilator <b>102</b> is inserted into the psoas muscle <b>172</b> such that the major axis <b>122</b> is oriented substantially parallel to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site and the minor axis <b>124</b> is oriented substantially perpendicular to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site. With the first dilator <b>102</b> inserted through the psoas muscle, an additional or secondary stimulating probe <b>170</b><i>a </i>may be inserted into the channel <b>126</b> to allow the surgeon determine the proximity of neural elements or nerves.

As shown in <figref idref="DRAWINGS">FIG. 9C</figref>, the surgeon may then rotate the first dilator <b>102</b> about the longitudinal axis <b>112</b> about 90° or about 270° (e.g., clockwise or counter clockwise) such that the major axis <b>122</b> is substantially perpendicular to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site and such that the minor axis <b>124</b> is substantially parallel to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site The stimulating probe <b>170</b><i>a </i>may be utilized before, during, and/or during rotating the first dilator <b>102</b> to transmit one or more electrical pulses via an EMG into the stimulating probe to determine the proximity of neural elements or nerves. For example, the first dilator <b>102</b> may be rotated so as to complete one or more rotations about the longitudinal axis <b>112</b> to enable the surgeon to locate a safe zone and/or determine the proximity of neural elements or nerves via the stimulating probe <b>170</b><i>a</i>. The insertion site is dilated or enlarged by the rotation of the first dilator <b>102</b> as a result of the major axis <b>122</b> of the first dilator <b>102</b> being greater than the minor axis <b>124</b> thereof. The stimulating probe <b>170</b><i>a </i>may be removed from the first dilator <b>102</b> after the first dilator <b>102</b> is rotated as described above.

As shown in <figref idref="DRAWINGS">FIG. 9D</figref>, the surgeon can insert the second dilator <b>104</b> over the first dilator <b>102</b> and towards the patient's spine <b>174</b> by receiving the first dilator <b>102</b> in the bore <b>140</b> of the second dilator <b>104</b> in a way that the minor axis <b>144</b> of the second dilator <b>104</b> is aligned with the major axis <b>122</b> of the first dilator <b>102</b> the major axis <b>142</b> of the second dilator <b>104</b> is aligned with the minor axis <b>124</b> of the first dilator <b>102</b>. This arrangement of the second dilator <b>104</b> relative to the first dilator <b>102</b> results in the distal end <b>136</b> of the second dilator <b>104</b> being initially inserted into the psoas muscle <b>172</b> so that the minor axis <b>144</b> of the second dilator <b>104</b> is oriented substantially perpendicular to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site and the major axis <b>142</b> is substantially parallel to the prevalent direction or orientation of psoas muscle fibers <b>176</b>. With the second dilator <b>104</b> inserted through the psoas muscle <b>172</b>, the stimulating probe <b>170</b><i>a </i>may be inserted into the channel <b>146</b> to allow the surgeon to determine the proximity of neural elements or nerves.

As shown in <figref idref="DRAWINGS">FIG. 9E</figref>, the surgeon may rotate the second dilator <b>104</b> about the longitudinal axis <b>132</b> about 90° or about 270° (e.g., clockwise or counter clockwise) such that the major axis <b>142</b> is substantially perpendicular to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site and such that the minor axis <b>144</b> is substantially parallel to the prevalent direction or orientation of psoas muscle fibers <b>176</b> adjacent to the insertion site. The stimulating probe <b>170</b><i>a </i>may be utilized before, during, and/or during rotating the second dilator <b>104</b> to transmit one or more electrical pulses via an EMG into the stimulating probe <b>170</b><i>a </i>to determine the proximity of neural elements or nerves. For example, the second dilator <b>104</b> may be rotated so as to complete one or more rotations about the longitudinal axis <b>132</b> to enable the surgeon to determine the proximity of neural elements or nerves via the stimulating probe <b>170</b><i>a</i>. The stimulating probe <b>170</b><i>a </i>may be removed after the second dilator <b>104</b> is rotated as described above.

The first dilator <b>102</b> is matingly received in the bore <b>140</b> of the second dilator <b>104</b> such that the second dilator <b>104</b> and the first dilator <b>102</b> move as a unit when the second dilator <b>104</b> is rotated. The insertion site is further dilated or enlarged by the rotation of the second dilator <b>104</b> as a result of the major axis <b>142</b> of the second dilator <b>104</b> being larger than the minor axis <b>144</b> of the second dilator <b>104</b>.

The surgeon can insert one or more second or intermediate dilators <b>104</b> in a similar manner and rotating each successive second dilator <b>104</b> about 90° or about 270° (e.g., clockwise or counter clockwise) after insertion.

As shown in <figref idref="DRAWINGS">FIG. 9F</figref>, the surgeon can insert the third or final dilator <b>106</b> over the second dilator <b>104</b>, for example, by slidably receiving the second dilator <b>104</b> in the bore <b>160</b> of the third dilator <b>106</b> such that the major axis <b>142</b> of the second dilator <b>104</b> is aligned with the major axis <b>162</b> of the bore <b>160</b> and the minor axis <b>144</b> is aligned with the minor axis <b>164</b> of the bore <b>160</b>. The second dilator <b>104</b> is matingly received in the bore <b>160</b> of the third dilator <b>106</b> such that the third dilator <b>106</b> and the second dilator <b>104</b> move as a unit when the third dilator <b>106</b> is rotated. With the third dilator <b>106</b> inserted through the psoas muscle <b>172</b>, the stimulating probe <b>170</b><i>a </i>may be inserted into the channel <b>166</b> to allow the surgeon to determine the proximity of neural elements or nerves by transmitting one or more electrical pulses via an EMG into the stimulating probe. For example, the surgeon may rotate the third dilator <b>106</b> between about 0° and about 360° (clockwise or counter clockwise) about the longitudinal axis <b>152</b> to enable the surgeon to determine the proximity of neural elements or nerves by transmitting one or more electrical pulses via an EMG into the stimulating probe <b>170</b><i>d. </i>

The third dilator <b>106</b> may interface with a retractor (not shown) that can be inserted over the third dilator <b>106</b> to subsequently retract the tissue and to permit removal of the dilation system <b>100</b> and the stimulating probes <b>170</b> and <b>170</b><i>a. </i>

As will be appreciated by persons of ordinary skill in the art, in some instances an external diameter of the dilators of dilation systems dictates the size of retractors that can be used with the particular dilation system. When the retractors have a relatively small diameter, generally smaller dilators are used to dilate the muscle prior to inserting the retractor. However, smaller diameter dilators may not have a sufficient thickness to accommodate a probe channel therein. This problem is especially relevant to the diameters of second and subsequent sequential dilators that are inserted over one another in a sequence. To address this issue, the first dilator may have an overall diameter configured to be as small as possible while still allowing the first dilator to accommodate a stimulating probe bore or channel therein. The second and subsequent dilators may be modified such that a portion of the respective stimulating probe channels extend into a bore for receiving the preceding dilator, thus resulting in a reduced overall diameter of each dilator and of the dilation system as a whole, while using a standard or fixed size stimulating probe.

Referring now to <figref idref="DRAWINGS">FIGS. 10-13</figref>, shown therein is an embodiment of a dilation system <b>100</b><i>a</i>. The dilation system <b>100</b><i>a </i>includes a first or initial dilator <b>180</b>, a second or intermediate dilator <b>182</b>, and a third or final dilator <b>184</b>. The dilation system <b>100</b><i>a </i>may be configured to be used in combination with a monitoring K-wire or stimulating probe for transmitting an electrical pulse as described above.

As shown in <figref idref="DRAWINGS">FIG. 11</figref>, the first dilator <b>180</b> includes an elongated body <b>188</b> having a longitudinal axis <b>190</b>, a bore <b>192</b>, and an outer surface <b>194</b>. The elongated body <b>188</b> can be implemented similarly to the elongated body <b>110</b>. The bore <b>192</b> may be implemented similarly to the bore <b>120</b> and is sized and configured to slidably receive a stimulating probe, such as the stimulating probe <b>170</b>. In one embodiment, the bore <b>192</b> may be omitted from the elongated body <b>110</b>.

The outer surface <b>194</b> has a substantially circular transverse cross-section but includes a channel <b>196</b>, a keying slot <b>198</b>, and a groove <b>200</b>. The outer surface <b>194</b> may taper at a distal end of the elongated body <b>188</b> to facilitate insertion into tissue. The general shape of the first dilator <b>180</b> is atraumatic.

The channel <b>196</b> may be implemented similarly to the channel <b>126</b> and is configured to slidably receive a stimulating probe therein, such as the stimulating probe <b>170</b><i>a</i>. The keying slot <b>198</b> is configured to receive a keying pin therein so as to key the orientations of the first dilator <b>180</b> and the second dilator <b>182</b> relative to one another. It is to be understood that the keying slot <b>198</b> may have any desired shape, size, or cross-section and may be located adjacent to a proximal end of the elongated body <b>188</b> or may extend partially or substantially completely along the outer surface <b>194</b> of the elongated body <b>188</b> in some embodiments so as to not cause trauma to tissues or interfere with dilating a surgical opening during use of the first dilator <b>180</b>.

The groove <b>200</b> is formed in the outer surface <b>194</b> and extends along the elongated body <b>188</b> such that the groove <b>200</b> may be aligned with a corresponding groove formed in the second dilator <b>182</b> as described below so as to form a combined lateral bore <b>202</b> (<figref idref="DRAWINGS">FIG. 10</figref>) for receiving a stimulating probe (e.g., the stimulating probe <b>170</b><i>a</i>). In some embodiments, the groove <b>200</b> is formed in the outer surface <b>194</b> so that the groove <b>200</b> is offset from the channel <b>196</b> at any desired distance or angle. In the embodiment shown in <figref idref="DRAWINGS">FIG. 11</figref>, the groove <b>200</b> is diametrically opposed to the channel <b>196</b> along the outer surface <b>194</b>, however, in some embodiments the groove <b>200</b> may be adjacent to, tangental to, or positioned at any desired location along the outer surface <b>194</b> relative to the channel <b>196</b>.

Referring now to <figref idref="DRAWINGS">FIG. 12</figref>, the second dilator <b>182</b> includes an elongated body <b>204</b> having a bore <b>206</b>, and an outer surface <b>208</b>. The bore <b>206</b> includes a groove <b>210</b> and a keying pin <b>212</b> formed therein and is sized, shaped, and configured to matingly and slidably receive the first dilator <b>180</b> therein so that the groove <b>210</b> aligns with the groove <b>200</b> of the first dilator <b>180</b> when the first dilator <b>180</b> is matingly received in the bore <b>206</b> such that the groove <b>210</b> and the groove <b>200</b> cooperate with one another to define the lateral bore <b>202</b> (<figref idref="DRAWINGS">FIG. 10</figref>) for receiving a stimulating probe, such as the stimulating probe <b>170</b><i>a</i>. As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, the grooves <b>200</b> and <b>210</b> are configured so that when a stimulating probe, such as the stimulating probe <b>170</b><i>a </i>is inserted into the lateral bore <b>202</b>, a portion of the stimulating probe <b>170</b> is received in the groove <b>200</b> and a portion of the stimulating probe <b>170</b> is received in the groove <b>210</b>. By way of example, the diameter of the stimulating probe <b>170</b><i>a </i>may be about 3 mm, while the general thickness of the elongated body <b>206</b> may in a range from about 1 mm to about 3 mm.

The keying pin <b>212</b> is configured to be matingly received in the keying slot <b>198</b> such that the first dilator <b>180</b> is matingly received in the second dilator <b>182</b> so that the groove <b>210</b> aligns with the groove <b>200</b> to form the lateral bore <b>202</b>.

The outer surface <b>208</b> includes a groove <b>214</b> and a keying slot <b>216</b>. The outer surface <b>208</b> may be tapered at a distal end of the elongated body <b>204</b> to facilitate insertion into tissue. The general shape of the second dilator <b>182</b> is atraumatic.

The groove <b>214</b> may be implemented similarly to the groove <b>200</b> and extends along the elongated body <b>204</b>, such that the groove <b>214</b> may be aligned with a corresponding groove formed in the third dilator <b>184</b> as described below so as to form a lateral bore <b>218</b> (<figref idref="DRAWINGS">FIG. 10</figref>) for receiving a stimulating probe therein. The groove <b>214</b> may be formed at any desired location in the outer surface <b>208</b>. In some embodiments, the groove <b>214</b> may be positioned along the outer surface <b>208</b> so that the groove <b>214</b> aligns with the channel <b>196</b> when the first dilator <b>180</b> is matingly received by the second dilator <b>182</b>.

The keying slot <b>216</b> may be implemented similarly to the keying slot <b>198</b> and is configured re receive a keying pin therein. The keying slot <b>216</b> may be positioned at any desired location and may be offset from the groove <b>214</b>, the keying pin <b>212</b>, and the groove <b>210</b> in some embodiments of the inventive concepts disclosed herein.

Referring now to <figref idref="DRAWINGS">FIG. 13</figref>, the third dilator <b>184</b> may be implemented similarly to the third dilator <b>106</b> and includes an elongated body <b>220</b> having a bore <b>222</b> and an outer surface <b>224</b>. The bore <b>222</b> may be implemented similarly to the bore <b>206</b> and includes a groove <b>226</b> and a keying pin <b>228</b>. The bore <b>222</b> is configured to matingly receive the second dilator <b>182</b> therein so that the groove <b>226</b> aligns with the groove <b>214</b> of the second dilator <b>182</b> when the second dilator <b>182</b> is matingly received in the bore <b>222</b> such that the groove <b>226</b> and the groove <b>214</b> cooperate with one another to define the lateral bore <b>218</b> (<figref idref="DRAWINGS">FIG. 10</figref>) for receiving a stimulating probe such as the stimulating probe <b>170</b> therein. By way of example, the diameter of the stimulating probe <b>170</b><i>a </i>may be about 3 mm, while the general thickness of the elongated body <b>220</b> may in a range from about 1 mm to about 3 mm.

Further, the keying pin <b>228</b> is matingly received in the keying slot <b>216</b> of the second dilator <b>182</b> so as to align the second dilator <b>182</b> and the third dilator <b>184</b> relative to one another as described above.

The outer surface <b>224</b> is configured so that the third dilator <b>184</b> interfaces with a retractor to subsequently retract the tissue and to permit removal of the dilation system <b>100</b><i>a </i>and the stimulating probes.

As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, the dilation system <b>100</b><i>a </i>may be implemented with any number of dilators for example two, three, four, or more.

Referring now to <figref idref="DRAWINGS">FIGS. 14-17</figref>, shown therein is another embodiment of a dilation system <b>100</b><i>b </i>constructed in accordance with the inventive concepts disclosed herein. The dilation system <b>100</b><i>b </i>includes a first or initial dilator <b>230</b>, a second or intermediate dilator <b>232</b>, and a third or final dilator <b>234</b> configured to be matingly coupled with one another. The dilation system <b>100</b><i>b </i>is configured to be used in combination with a monitoring K-wire or stimulating probe, such as the stimulating probe <b>170</b>, for transmitting an electrical pulse.

Referring now to <figref idref="DRAWINGS">FIG. 15</figref>, the first dilator <b>230</b> includes an elongated body <b>240</b> having a longitudinal axis <b>242</b>, a bore <b>244</b>, and an outer surface <b>246</b>. The bore <b>244</b> may be implemented similarly to the bore <b>120</b> and is configured to slidably receive a stimulating probe such as the stimulating probe <b>170</b> therein.

The outer surface <b>246</b> includes a channel <b>248</b> and a groove <b>250</b>. The channel <b>248</b> may be implemented similarly to the channel <b>126</b> and is configured to slidably receive a stimulating probe therein. The groove <b>250</b> may be implemented similarly to the groove <b>200</b> and is configured to receive a portion of the second dilator therein as described below.

Referring now to <figref idref="DRAWINGS">FIG. 16</figref>, the second dilator <b>232</b> includes an elongated body <b>252</b> including a sidewall <b>254</b>, a bore <b>256</b>, an outer surface <b>258</b>, and a channel <b>260</b>. The sidewall <b>254</b> has a thickness <b>262</b>. The bore <b>256</b> may be implemented similarly to the bore <b>206</b> and is configured to matingly receive the first dilator <b>230</b> therein.

The channel <b>260</b> is formed in sidewall <b>254</b> of the elongated body <b>252</b>. In some embodiments, the channel <b>260</b> is sized and configured to receive a standard or fixed size stimulating probe, such as the stimulating probe <b>170</b><i>a</i>, and has a diameter <b>264</b> which is larger than the thickness <b>262</b> of the sidewall <b>254</b> such that a bridge portion <b>266</b> of the sidewall <b>254</b> extends inwardly into the bore <b>256</b>. The bridge portion <b>266</b> is configured to be matingly received in the groove <b>250</b> when the second dilator <b>232</b> is positioned over the first dilator <b>230</b>. By way of example, the diameter of the stimulating probe <b>170</b><i>a </i>may be about 3 mm, while the general thickness of the sidewall <b>254</b> of the elongated body <b>252</b> may in a range from about 1 mm to about 3 mm.

The outer surface <b>258</b> includes a groove <b>268</b>. The groove <b>268</b> may be implemented similarly to the groove <b>250</b> and is configured to receive a portion of the third dilator <b>234</b> therein as described below. As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, in some embodiments the groove <b>268</b> may be offset from the channel <b>260</b> along the outer surface <b>258</b> at any desired angle or distance.

Referring now to <figref idref="DRAWINGS">FIG. 17</figref>, the third dilator <b>234</b> may be implemented similarly to the second dilator <b>232</b> and includes an elongated body <b>270</b> including a sidewall <b>272</b>, a bore <b>274</b>, an outer surface <b>276</b>, and a channel <b>278</b>. The elongated body <b>270</b> may be implemented similarly to the elongated body <b>252</b> described above. The sidewall <b>272</b> has a width <b>280</b>. The bore <b>274</b> may be implemented similarly to the bore <b>256</b> and is configured to matingly receive the second dilator <b>232</b> therein. The channel <b>278</b> is formed in sidewall <b>272</b> of the elongated body <b>270</b> and is sized and configured so as to receive a standard or fixed size stimulating probe, such as the stimulating probe <b>170</b><i>a</i>. The channel <b>278</b> has a diameter <b>282</b> which is larger than the width <b>280</b> of the sidewall <b>272</b> such that a bridge portion <b>284</b> of the sidewall <b>272</b> extends inwardly into the bore <b>274</b>. By way of example, the diameter of the stimulating probe <b>170</b><i>a </i>may be about 3 mm, while the general thickness of the sidewall <b>272</b> of the elongated body <b>270</b> may in a range from about 1 mm to about 3 mm. The bridge portion <b>284</b> is configured to be matingly received in the groove <b>268</b> when the second dilator <b>232</b> is matingly inserted into the bore <b>274</b>. As will be appreciated by persons of ordinary skill in the art having the benefit of the instant disclosure, due to the groove <b>268</b> being offset from the channel <b>260</b> as described above, the channel <b>278</b> is offset from the channel <b>260</b>.

From the above description, it is clear that the inventive concepts disclosed and claimed herein are well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. While exemplary embodiments of the inventive concepts have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the inventive concepts disclosed and claimed herein.